Oil pressure switch



Jan. 4, 1955 G. B. sHAw 2,698,887

OIL PRESSURE SWITCH Filed June 19, 1952 (am, 1W* L J His Arm/Mfrs United States Patent O OIL PRESSURE SWITCH George B. Shaw, Anderson, Ind., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application June 19, 1952, Serial No. 294,437

3 Claims. (Cl. 200-83) This operation relates to fluid operated switches for electrical circuits and more particularly to an On-Off electric indicator to be operated by oil pressure in an internal combustion engine. l y

An important use of this invention is in connection with a signal light which is caused to burn when the ignition circuit is closed. The switch is associated with the oil feed line of an internal combustion engine. When the engine is operating and the pressurefin the oil line is above a predetermined value the switch will be moved to open the circuit to the signal lamp, but should the oil pressure be below a predetermined value or when the engine is not running the circuit to the signal lamp will be closed so long as the ignition circuit is closed.

An object of the present invention is to provide such a switch having a switch actuating element which has adequate movement to compensate for wear and inaccuracies in the manufacture of parts.

Another object is to provide a switch with means for positively limiting the movement of the diaphragm when actuated by fluid pressure to prevent distortion thereof.

Another object of the invention is the provision of a fluid operated switch assembly of simple construction; easily assembled and thoroughly reliable in operation.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawing:

Fig. 1 is an end view of the switch.

Fig. 2 is a sectional view taken on line 2-2 of Fig. 1 and showing the switch in its normal position.

Fig. 3 is a sectional View similar to Fig. 2, but showing the switch in its actuated position.

Fig. 4 is a sectional view taken on line 4-4 of Fig. 2.

Referring to the drawing designates a switch unit for controlling an indicator or lamp 21 in accordance with the pressure, of lubricating oil from a pressure pump. When the oil supply is inadequate the switch completes an electrical circuit between a terminal 22 and a fitting on coupling 25 which is grounded.

Referring to Figs. 2 and 3, the switch unit 20 includes the fitting 25 which is adapted to be connected with an oil pressure line through an oil passage 26 that leads into a chamber 27. Chamber 27 is formed by a shell 28 and a diaphragm 29 made of impervious rubber-like material, for example Fairprene or other suitable material which is resistant to attack by lubricating oil. The periphery of the diaphragm 29 together with a ring contact 30 are clamped between a flange 31 of shell 28 and an outwardly extending flange 32 of a cup-shaped casing 33, the flange 32 being bent around the flange 31 as indicated at 34. Said diaphragm divides and seals oil a part of the casing 33 to form a switch compartment. In order to form a fluid tight seal for the chamber 27 the flange 31 of shell 28 has an annular bead 35 formed thereon which will be embedded near the periphery of the diaphragm 29 when the parts are assembled. The ring contact has a central inturned flange 36 and the flange is so formed as to provide a smooth curved surface 37 which backs up the diaphragm and also prevents the diaphragm from being marred or damaged when the diaphragm is exposed to fluid pressure.

A cup-shaped contact 40 is located on the opposite side of the chamber 27 and maintained in engagement lill Patented Jan. 4, 1955 rice with the central portion of the diaphragm by a spring 41. In this instance the contact 40 is of stepped formation and includes a reduced portion 42 and a larger portion 43 to provide a shoulder 44. The reduced portion 42 passes :freely through the llange 36 of the ring 30 so that the shoulder 44 makes contact engagement with the rim of the flange 36. The spring 41 which holds the contact 40 against the diaphragm has one end seated in the reduced portion 42 while the other end engages a metal washer 45 located within a cup-shaped member 46 of molded insulating material. The member 46 includes an outer cylindrical wall 47 and an inner casing wall 48. A plurality of ribs 50 extend between the walls to provide rigidity to the member 46. The bottom wall of housing 33 and an insulating washer 51 are clamped together between a shoulder 52 of the terminal 22 and the riveted end 53 of said terminal.

Normally the spring 41 as viewed in Fig. 2 urges the contact 40 to the right sok that the shoulder 44 makes contact engagement with the rim of the flange 36 so that the switch completes an electrical circuit between the terminal 22 and the fitting 25. The circuit completed through the switch unit 20 is as follows: battery 60, lamp 21, ter minal 22, metal washer 45, spring 41, contact 40, contact ring 30, housing 33 and 28 and fitting 25 which is grounded. After the engine has started, and if oil supply is adequate, the engine driven oil pump will build up pressure within the oil feed line with which the fitting 25 is attached to a value sufficient to move the diaphragm 29 to the left against the tension of spring 41 causing the shoulder 44 to leave the flange 36 to open the circuit. The shoulder portion 44 of the contact 40 cooperates with the rim of the casing wall 48 of member 46 to limit the throw of the diaphragm when exposed to fluid pressure. The lamp will then be disconnected from the circuit.

When the safety switch or unit 20 is connected in the oil pressure system of an internal combustion engine the fitting 25 of safety switch is connected in a pipe line between a gear type oil pump, not shown, and a part to be lubricated. When the engine is not in operation the safety switch is moved to its normal position by the spring 41 which will cause the shoulder 44 of contact 40 to engage the rim of flange 36 as shown in Fig. 2. When the engine starts and if the oil supply is adequate the engine driven oil pump will build up pressure within the oil line with which the fitting 25 is connected to a valve sufficient to move the diaphragm to the left against the action of spring 41 thereby causing the contact 40 to leave the flange 36 and open the circuit. A vent opening 61 and a vent opening 62 in the member 46 and the casing 33, respectively are provided to insure the maintenance of substantially atmospheric pressure within the chamber 63 or dry side of the unit irrespective of movements of the diaphragm and temperature changes.

The spring 41 is so constructed that the switch will open at a minimum oil pressure for example lO p. s. i. This pressure will be maintained even while the engine is idling if oil pressure is adequate. So long as the lamp does not burn the oil pressure is adequate. When the amount of lubricating oil in the crankcase of the engine is too low for safe engine operation the pressure against the diaphragm 29 will fall below the l0 p. s. i.' for example, the spring 41 will cause the contact 40 and diaphragm to move to the right causing the contact 40 to engage contact 30 and cause the lamp to be connected in a circuit and burn to indicate to the operator that oil should be added to the crankcase or the pressure system should be checked and serviced.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

l. In a fluid pressure operated switch, a chamber having a stationary wall; a body of insulating material located within the chamber, a terminal for securing the body to the stationary wall, the inside of the body having an annular channel thereby forming annular walls with the rim of the inner wall located in a plane below the plane of the rim of the outer wall; a diaphragm forming the opposite wall of the chamber; a grounded terminal extending across said chamber immediately inside the diaphragm and having a"cent`ral"opening;` actin-shaped" bridging member extending across the inner annular wall of the body, and guided axially by the outer wall of the s-idbridgin'gmember Vhaving', a central portio'nf'p'rooperatingy with `said inner' annularV wall to liinitfthe axial" movement ofthe bridging member-andi thelieby'` prevent excessive-` distortion of the diaphragm.

tiilayy wall; a body'of insulatingimaterial located within theJ chamber, said fbodyiincludingf aj central' :skirt portion;y a terminal exposedwithin the skirt for securing' the body tothe stationary wall; annLmetallic diaphragm forming theopposite' wall of `the ch2'1mber;` a" grounded'v terminal' extendingl across said-chamber adjacent the inside ofthe diaphragmand"havingf'an opening; a contact extending" over the`sk1rt, and the-opening offgroundedterminal so` ast be actuated bythediaphragm;` a spring forlestablishing an electrical connection between the terminal andthe coiitaetYandalso for urging the contact into engagement with-"the grounded terminal, said contactV beingr ofV a diam-y ete'' greater than` the-skirt", said skirt cooperating vwith the Contact to limit the axial movement thereof and thereby 2 prevent excessive stretch of the diaphragm:

3'; A uid pressure comprising, a\two` part metallic cas-` ing, said parts clamping between them a ring contact and tion toopen a. circuit; and.l a conducting spring interposed between-the terminaliand the movable Contact `for urging the movable Contact in the opposite directionfwheieby exing of the diaphragm permits the movable contact to move into contacten'gagement" wlitha th. stops of--the ring contact to establish a circuit between terminal and the casing.

References Cited in the le of this patent UNI-TED` STATES lfvAIEVN'ISly 

